1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a semiconductor device that includes a vertical Hall element configured to detect a magnetic field in a horizontal direction.
2. Description of the Related Art
A Hall element is capable of detecting position or angle without contact as a magnetic sensor, and accordingly has various uses. While magnetic sensors that use a horizontal Hall element configured to detect magnetic field components perpendicular to a semiconductor substrate surface (vertical magnetic field) are particularly well known, there have been proposed various magnetic sensors that use a vertical Hall element configured to detect magnetic field components parallel to a substrate surface (horizontal magnetic field).
A vertical Hall element is generally configured to detect a horizontal magnetic field by utilizing both of a current that flows in a direction perpendicular to a substrate and a current that flows in a direction parallel to the substrate.
Meanwhile, in recent years, there has been proposed the following vertical Hall element, which is disclosed in Japanese Patent No. 5966060, for example. In the vertical Hall element, a current that flows in a direction perpendicular to a substrate is reduced while a current that flows in a direction parallel to the substrate is increased, and the vertical Hall element is configured to detect a horizontal magnetic field by positively utilizing the increased current in the direction parallel to the substrate.
The vertical Hall element disclosed in Japanese Patent No. 5966060 includes trenches formed in the semiconductor substrate, an insulating film formed on the inner side surface of each of the trenches, a conductor embedded in each of the trenches via the insulating film, and a high-concentration contact region connected to the conductor and formed in the bottom portion of each of the trenches. The conductor embedded in each of the trenches and the contact region connected thereto function as a drive current supply electrode.
In such a configuration, when a current is supplied between two drive current supply electrodes, the current flows between the contact regions formed in the bottom portions of the trenches. Hence, this configuration can almost completely eliminate current components in the direction perpendicular to the surface of the substrate and cause most of the current to flow in the direction parallel to the surface of the substrate.
The structure of Japanese Patent No. 5966060, however, has a problem given below.
As described above, when a current is supplied between the two drive current supply electrodes, most of the current flows in the direction parallel to the surface of the substrate. This current (flow) concentrates in particular along the shortest path between the contact regions in the semiconductor substrate, which is a magnetism sensing portion. This means that almost no current flows to regions of the magnetism sensing portion that are located below the contact regions and are near the rear surface of the substrate. Further, the insulating film is formed on the inner side surface of the trench, in which the conductor of the drive current supply electrode is embedded, and hence the current hardly flows to a region of the magnetism sensing portion that is located between the side walls of the two trenches. As a result, the current that flows in the direction parallel to the substrate has a small width in a depth direction of the substrate.
The magnetic sensitivity of a Hall element is known to rise in proportion to the width of a current that flows through the Hall element. In the structure of Japanese Patent No. 5966060, however, the width of the current that flows in the direction parallel to the substrate is small as described above, and as a result, the sensitivity is only slightly improved.